Manufacture of hard rollers



Oct. 19, 1943. J. GORDON MANUFACTURE OF HARD ROLLERS Filed Sept. 27. 1941 I IIII/IIIIIIIII INVENTOR -71 601E150 BYW 1 ATTORNEY Patented on. 19, 1943 Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application September 27, 1941, Serial No, 412,560

10 Claims.

This invention relates to the manufacture of hard rollers and more particularly to such made of hard carbide, such as tungsten carbide mixed with a small proportion of binding material, such as cobalt.

The principal object of my invention generally considered, is the manufacture of hard carbide rollers, and more particularly to such made of material such as cobalt as a binding agent, and improvement on the conventional method which is relatively wasteful.

Another object of my invention is the production of hard carbide rollers .by making them initially in cylindrical form, rather than first pressing them square in section and then turning to cylindrical form.

A further object of my invention is the manufacture of hard carbide rollers by pressing the same initially to cylindrical form, as by applying hydraulic pressure to the powdered material when disposed in a hollow cylinder of approximately the desired interior size, then heating in said cylinder and causing shrinkage of the produced ingot, whereby the latter is readily removable. a

A still further object of my invention is the completion of the hard carbide roller from an ingot, such as described in the preceding paragraph, by further heat treating said ingot at a higher temperature, then truing the ends as by grinding, and brazing a cold rolled steel centering cylindrical member at each end, placing in a lathe, and grinding true to size.

but showing the mold completely filled and with an hydraulic plunger about to compress the material to the desired preliminary density.

An additional object of my invention is the manufacture of hard rollers in such a 'manner that very little finishing is necessary, that is, the mere grinding off of not more than 55 inch after the ingot has been made by pressing, baking and sintering.

Other objects and advantages of the invention, relating to the particular arrangement and construction of the various parts, will become apparent as the description proceeds.

Referring to the drawing:

Figure 1 is a perspective view of a completed roller embodying my invention,

Figure 2 is a plan of one form of mold in which powdered hard material may be compressed to make an ingot for one of my rollers.

Figure 3 is a vertical sectional view on the line III-III of Figure 2, in the direction of the arrows, also showing powdered carbide material being added to the mold to bring it up to the desired level. I

Figure 4 is a view corresponding to Figure 3,

Figure 5 is a view corresponding to Figure 2, but showing a modification.

Figure 6 is a fragmentary view of a portion of a furnace used for heating the mold and carbide contained therein, the mold being shown after having been withdrawn from the furnace and partly broken away to indicate a shrinkage of the produced ingot away from the mold.

Figure '1 is a view of the ingot after removal.

from the mold and in the process of having an end finished by grinding.

Figure 8 is a fragmentary view of one end of the roller after the same has been ground true and a centering cap brazed thereto, but before the cylindrical surface has been ground true.

In the ordinary process of making rollers from hard carbide materials, such as tungsten carbide using material such as cobalt as a binding agent,

the mixed carbide powder was pressed to' a 1" square ingot, 8" long, said ingot baked in carbon and fired in hydrogen and then placed in a lathe and turned to %"'diameter. A set of rollers made by this process proved far superior to steel rollers for the purpose of making tungsten sheet. The cost of producing such rollers, however, was exceedingly expensive and in order to decrease such expense: I have devised an improved process by which a large proportion of the cost previously found necessary in the manufacture has been saved.

In accordance with my process, tungsten carbide and cobalt are mixed together in the desired proportion in finely powdered form and placed in a cylindrical mold, preferably made of 1" inside diameter seamless steel, with a V wall.

Such tubing is indicated by the reference character H) in Figure 5, the powder mixture being designated by thereference character ll.

The proportion of the ingredients depends on the hardness desired. If, for example, the material is to be used for making small dies rather than rollers, I may employ from 4 to 10% of cobalt and the balance tungsten carbide, the latter material being desirably manufacturedin accordance with my pending application, Serial No. 333,919, filed May 8, 1940, and owned by the assignee of the present application. In accordance with said application, I make substantially pure tungsten carbide by first forming a mixture consisting of 92.75% tungsten powder and 7.25% carbon powder, and then heat in a hydrogen atmosphere to cause the ingredients to combine,

with not more than .03% free carbon, to approximate the chemicalcompound WC. If, however, large dies or rollers are being manufactured, I desirably employ a mixture of 13% fine- 1y divided cobalt powder and 87% finely divided tungsten carbide powder. may be produced by reducing the powdered oxide,.obtained from any suitable source, in hydrogen.

If, however, it is impossible to secure the desired seamless steel tubing, a mold l2 may be produced, as illustrated in Figures 2 and 3, that is by cutting some steel tubing longitudinally, as indicated at l3 and H, to produce the two halves I5 and 6, said halves being held together to produce a cylindrical mold by clamps l1, l8 and I9, shims 2| and 22 being applied between the abutting surfaces of the mold parts I5 and I6 in order' to insure that the interior of the mold is accurately cylindrical.

Such a mold, set up as shown in Figure 3, has a cylindrical plug 23 positioned in the lower end thereof and accurately fitting the same, as indicated. If the mold is formed 1" inside diameter and 4%" long, as in a preferred embodiment of my invention, the plug 23 is desirably about 1" long and inserted so as to leave about initially projecting from the mold. After filling the mold with powder of the desired composition, as illustrated in Figure 3, another similar plug 24 is applied and pressed down in place by hand, so that about /1" may project therefrom.

The assembled mold, powder and plugs are then placed under the plunger 25 of a hydraulic press, and the ram thereof depressed until the upper surface of the upper plug 24 is flush, or approximately flush, with the top of the mold l2. The pressure is released, the mold reversed, and the operation repeated on the plug 23 until that is flush, or approximately flush, with the corresponding end of the mold. In this way the density of the compressed carbide is made substantially uniform throughout the mold.

The powder is further compressed from one, and then from the other end, as by allowing the plunger 26 from the press to exert pressure on the contents of the mold l2, until the material has been compressed as much as possible with the available hydraulic pressure of ten tons. This, it will be seen, in accordance with the preferred embodiment described, amounts to a pressure of about 8.1 tons per square inch.

If a press which acts from both ends is available, the plugs 23 and 24 may be simultaneously pressed from opposite ends of the mold to the limit of the desired pressure. v

The mold and its pressed powdered material with the plugs in place, is then removed from the press and placed in furnace 21 where it is baked'at about 1100 C. for about one-half hour. A desirable furnace is one electrically fired and consisting of molybdenum-wound alundum tubing operating in a hydrogen atmosphere. A hydrogen or other non-oxidizing or inert atmosphere is necessary in order to avoid oxidation of the. mold and its contents.

. The baking operation in the furnace 21 described, causes the ingot 28 to shrink from the mold i2, as represented in Figure 6, whereby upon removal of the plugs 23 and 24 the ingot will drop out if the mold is tilted.

'The baked ingot has a reasonable amount of strength but is not yet sintered to its final condition. In order to accomplish this sintering operation, it is packed in carbonaceous powder, such The cobalt powderas lamp black, and fired at a temperature of about 1450? C. for approximately one-half hour. This operation may be accomplished in an electric furnace, such as described in my application, Serial No. 333,919, previously referred to. However, any furnace creating a temperature of from 1420 to 1440 or 1450 C. and containing a nonoxidizing or inert atmosphere, may be employed. In order, however, to prevent decarbonization of the roller, the same is packed in finely divided I relatively pure carbon.

After this second baking or sintering operation, the ingot is allowed to cool, removed from the furnace, and its ends trued, asindicated in Figure 7, as by grinding on an emery or carborundum wheel 29, as shown in Figure 7.

In order to finally finish the roller, it is necessary to place the same in a lathe and grind the cylindrical surface thereof. In order to accurately center the same in such a lathe, it is desirable to place end members 3| and 32 thereon, as shown most clearly in Figures 1 and 8. These end members are in the form of cold rolled steel cylinders, center punched, as indicated at 33, and of a diameter corresponding with that of the roller ingot- 28. These end members are desirably brazed to the roller ingot by applying a disk 34 of copper against the inner surface of the end member, say that designated 3|, when the same is disposed with its punched surface down. This copper disk 34 may be approximately .04" thick and have applied thereover, a brass disk 35, preferably .002" thick. The roller ingot 28 is then accurately aligned therewith and placed thereon, and the assembly disposed in a furnace while maintaining the axis thereof vertical. While in said furnace, it is heated to a temperature of about 1080" C. which causes the end member 3| to be securely brazed to the engaging end of the roller ingot 28.

To secure the end member 32 to the other end of the ingot, the latter is inverted over said member with corresponding copper and brass disks disposed in a similar manner and heated in a similar furnace, care, however, being taken that the end already brazed, either protrudes from the furnace or is protected from heat enough to melt the brazing material and cause loosening of the member 3| from the ingot.

After the foregoing brazing operations have been completed, the assembled roller, including the parts 28, 3| and 32, is placed in a lathe, centered by the punches 33, and ground while rotating so that the assembly becomes accurately cylindrical. On account of the accurate way in which the roller ingot has been made and assembled, it is found in practice that it is only ordinarily necessary to grind off about .003" in order to. produce an accurately cylindrical roller.

Rollers produced by the aforedescribed process have been employed to satisfactorily turn out thin tungsten sheets which could not be purchased.

Although preferred embodiments of my invention have been disclosed, it will be understood that modifications may be made within the spirit and scope of the appended claims.

I claim:

1. The method of making hard rollers, comprising placing tungsten carbide, approximatingv the chemical compound WC, with from 4 to 13% cobalt, both in powdered form in a hollow cylinder of the desired size, forcing a plunger in an end of said cylinder to compress said material,

heating said material in said cylinder, causing the former to shrink, removing the ingot produced from the cylinder, and sintering at a higher temperature to increase its strength.

2. The method of making hard-rollers, comprising placing tungsten carbide powder mixed with a small proportion of a binder in powdered form in a metal cylinder, forcing a, plunger in an end of said cylinder to compress said material, firing said material at about 1100 0., thereby causing the produced ingot to shrink from the cylinder, removing said ingot, and firing at about 1450" C.

3. The method of making hard rollers, comprising placing tungsten carbide powder in a metal cylinder, forcing a plunger in an end of said cylinder to compress said material, firing said material in said cylinder at about 1100 0., thereby causing the produced ingot to shrink from the cylinder, removing said ingot, and firing at about 1450" C.

4. The method of making hard rollers, comprising placing a homogeneous mixture of tungsten carbide and a desired proportion of cobalt, both in powdered form, in a metal cylinder, inserting a plunger in an end of said cylinder, compressing said material by means of said plunger, heating said cylinder and enclosed material at about 1100 C. thereby causing the,

produced ingot to shrink from the cylinder, removing said ingot from said cylinder, and firing at about 1450".

5. The method of making hard rollers, comprising placing a tungsten carbide mixture in powdered form in a seamless steel tube, forcing plungers in the ends of said tube to compress said material, firing at about 1100 0., thereby causing the ingot to shrink from the cylinder and facilitate removal, removing said ingot, and firing at about 1450 C.

6. The method of making hard rollers, comprising placing a tungsten carbide mixture in powdered form in a seamless steel tube about 1" inside diameter and approximately 4 long, inserting a plunger in one end of said tube while supporting the other end, applying hydraulic pressure to said plunger, heating the material to about 110d C. thereby causing the produced ingot to shrink from the tube, removing said ingot from said tube, and heating to about 1450.

7. The method of making hard rollers, comprising placing a-tungsten carbide mixture in powdered form in a metal cylinder, forcing a plunger in an end of said cylinder to apply a pressure of more than eight tons per square inch to said material, firing said material at about 1100 0., thereby causing the produced ingot to shrink from the cylinder, removing said ingot, and firing at about 1450" C.

8. The method of making hard rollers, comprising placing tungsten carbide powder in a metal cylinder, forcing aplunger in an end of said cylinder to apply a pressure thereto of more than eight tons per square inch, firing said material in said cylinder at about 1100 0, thereby causing the produced ingot to shrink from the cylinder, removing said ingot and firing at about 1450 C.

9. The method of making hard rollers, comprising placing a homogeneous mixture of tungsten carbide and a desired proportion of cobalt, both in powdered form, in a metal cylinder, inserting a plunger in an end of said cylinder, placing said material 'under a pressure of more than eight tons per square inch by means of said plunger, heating said cylinder and enclosed material at about 1100 C. thereby causing the produced ingotto shrink from the cylinder, removing said ingot from said cylinder, and firing at about 1450 C.

10. The method of making hard rollers, comprising placing a tungsten carbide mixture in powdered form in a seamless steel tube about 1" inside diameter and approximately 4 long, inserting a plunger in one end of said tube while supporting the other end, applying hydraulic pressure of ten tons to said plunger, repeating the operation from the other end to obtain substantially uniform density, heating the material to about 1100 C. thereby causing the produced ingot to shrink from the tube, removing said ingot from said tube, and heating to about 1450 C. for about one half hour.

JOSEPH GORDON. 

